LNG海工装备薄膜型液货舱晃荡周期与晃荡载荷研究

Study on the Sloshing Period and Sloshing Load of Membrane Liquid Cargo Tank on LNG Offshore Equipment

针对液化天然气(Liquefied Natural Gas,LNG)海工装备的薄膜型液货舱晃荡问题,按照挪威船级社(Det Norske Veritas,DNV)的规范,以4#液货舱为研究对象进行规范计算,由此得到各装载深度下的船体自身固有周期、舱内液体运动固有周期和液货舱晃荡载荷。比较船体自身固有周期与舱内液体运动固有周期,检验其是否符合规范要求;比较规范计算和模型试验所得液货舱晃荡载荷,检验模型试验是否可靠。经过这些比较发现:在某些装载深度下,船体自身固有周期与舱内液体运动固有周期比较接近,有引起液货舱内液体共振和砰击的风险;模型试验所得结果与砰击压力规范值较接近,是比较可靠的;考虑到共振和砰击的风险,后续的校核工作应重点关注砰击压力,并对液货舱结构作相应的加强。为今后改进建造LNG海工装备,建议针对液货舱内液体的共振和砰击进行更多、更细致的模型试验。

To solve the sloshing problem of membrane liquid cargo tank onboard a Liquefied Natural Gas (LNG) offshoreequipment, its NO.4 tank is taken as the example to perform the regulation calculation according to the Det NorskeVeritas (DNV) rules to obtain the natural period of the ship under different loading depth, the natural period of the liquidinside tank and the sloshing load. The ship natural period and the liquid motion period are checked to make sure theymeet the regulation then the sloshing loads obtained from regulation calculation and model experiment are compared tosee if the model test is reliable. Through these comparisons, it discovers that the ship natural period is close to the liquidnatural period under certain loading depth, which might cause liquid resonance and slamming impact inside the tank. Theresults of model test are close to the slamming pressure value specified by the rules, and are considered reliable. As thereis the risk of resonance and slamming impact, subsequent work should focus on the slamming pressure and the structuralreinforcement of the liquid tank. It is suggested to carry out more refined model tests to study the resonance andslamming inside liquid tanks for the future construction of LNG offshore equipment.